1 files changed, 48 insertions, 0 deletions
diff --git a/modules/language/python/hash.scm b/modules/language/python/hash.scm
new file mode 100644
index 0000000..ca5e32e
--- /dev/null
+++ b/modules/language/python/hash.scm
@@ -0,0 +1,48 @@
+(define-module (language python hash)
+  #:use-module (oop goops)
+  #:use-module (oop pf-objects)
+  #:export (py-hash complexity xy pyhash-N))
+
+(define-syntax-rule (aif it p x y) (let ((it p)) (if it x y)))
+
+(define N #xefffffffffffffff)
+(define pyhash-N N)
+
+(define-inlinable (xy v seed)
+  (modulo
+   (logxor seed
+           (+ (py-hash v)
+              #x9e3779b9
+              (ash seed 6)
+              (ash seed -2)))
+   N))
+
+(define complexity 10)
+
+;; The default is to use guile's hash function
+(define-method (py-hash x) (hash x N))
+
+(define-method (py-hash (x <pair>))
+  (define i 0)
+  (let lp ((x x))      
+    (if (< i complexity)
+        (begin
+          (set! i (+ i 1))
+          (if (pair? x)
+              (xy (lp (car x)) (lp (cdr x)))
+              (py-hash x)))
+        0)))
+         
+(define-method (py-hash (x <vector>))
+  (let ((n (min complexity (vector-length x))))
+    (let lp ((i 0) (s 0))
+      (if (< i n)
+          (lp (+ i 1)
+              (xy (py-hash (vector-ref x i)) s))
+          s))))
+
+(define-method (py-hash (x <p>))
+  (aif it (ref x '__hash__)
+       (it)
+       (hash x complexity)))
+